A federal judge on Thursday declined a request by US President Donald Trump’s former campaign manager Paul Manafort to suppress evidence seized by investigators for special counsel Robert Mueller’s office from a storage unit.

Manafort, who is currently jailed in Virginia, had argued that the evidence was seized improperly after an FBI agent got one of his employees to open the storage unit, rather than asking Manafort for permission or seeking a warrant.

But Judge Amy Berman Jackson for the US District Court for the District of Columbia rejected that argument, saying “law enforcement agents do not need a warrant to enter a location if they have voluntary consent”.

Manafort is facing two indictments in Washington and Virginia that arose from Mueller’s continuing investigation into potential collusion between Trump’s 2016 campaign and Russia.

He has pleaded not guilty to charges that range from conspiring to launder money and failing to register as a foreign agent for the pro-Russia Ukraine government, to bank and tax fraud.

Last week, Jackson ordered Manafort be jailed after Mueller brought fresh charges against him alleging he tampered with witnesses.

Manafort, 69, has been seeking ways to deprive prosecutors of what could be pivotal evidence in his Washington trial scheduled for September.

In a hearing last month, his lawyers told Jackson that his rights against unreasonable search and seizure under the US Constitution’s Fourth Amendment were violated in 2017 when the FBI searched the storage locker and also conducted a raid on his home in Alexandria, Virginia.